Thank's for your reponse
Internet speed is 100m/b up/down because is in datacenter.

Drocona if I understand the server calculate per core frequence and not by a total processor frequence ?
Do you think, bi processor bring a performence (for srcds), or decelerated the systeme for exemple Bi-Xeon?

Yes, that's correct, we calculate per core, this is because the SRCDS process is NOT multi threaded (use 2 or more cores at the same time).

The more cores and the faster they are, the more slots you can host. If I had to choose between Xeon and Core2Duo, I have no idea, go with the most handy and cheapest one, a Dualcore Xeon 2,4GHz is about the same performance as a Core2Duo 2,4Ghz.